Vanadium Loss Research Articles

Separation of V(Ⅴ) and Cr(Ⅵ) from vanadium-containing solutions based on E-pH diagrams of V-Cr-S-H2O system

The extremely similar physicochemical properties of vanadium and chromium lead to the difficulty in separating from each other. In this study, a novel hydrometallurgical process was devised to selectively precipitate chromium from vanadium-containing solutions, facilitating the efficient separation of V(V) and Cr(VI) while enabling the recovery of both vanadium and chromium species. The speciation of vanadium and chromium in solutions was investigated through the construction of E-pH diagrams for V-Cr-S-H2O system at 298 K, 363 K, and 453 K. The results revealed that under conditions of pH approximately 12 and temperature 363 K, the reduction potential of SO42-/S2- was found to lie between that of CrO42-/Cr(OH)3 and VO43-/V2O3. This suggests that selective reduction of Cr(VI) could be achieved using S2- as reducing agent. In order to validate the theoretical findings, single-factor experiments were conducted on a laboratory scale. The effects of various parameters including initial pH, sodium sulfide dosage, reaction time, temperature, and initial concentration of vanadium-containing solutions on the chromium precipitation ratio and vanadium loss ratio were investigated. The experimental outcomes showed that the chromium precipitation ratio reached 99.8 % while the vanadium loss rate was only 3.5 % when the experiment was conducted at the optimal conditions: the initial pH was set to 12, sodium sulfide dosage was 2.0 times of the theoretical dosage, reaction time was 60 min and the temperature was 363 K. Then, the chromium concentration in the solution decreased from 2407 mg/L to 3.3 mg/L. Ultimately, V2O5 with a purity of 99.0 % and Cr2O3 with a purity of 97.2 % were successfully obtained.

Research on V2O3 preparation by stepwise catalysis solution-phase hydrogen reduction from shale V-rich solution

Solution-phase hydrogen reduction reaction (SpHR) was introduced to overcome the problems of ammonia nitrogen pollution, high energy consumption, and long production flow of traditional reduction roasting. From φ-pH diagram, the increase of reaction temperature, vanadium concentration and H2 partial pressure is beneficial to the preparation of V2O3. High purity V2O3 could not be prepared by single addition catalysis and synchronous catalysis in SpHR process, and the Ni + NiSO4 stepwise catalysis can effectively eliminate the problem of nickel wrapped in vanadium precipitates during the precipitation process. Under the optimal conditions of Ni + NiSO4 stepwise catalysis of nickel powder dosage 5 g/L, NiSO4 dosage 8 g/L, nickel powder catalytic time 90 min, NiSO4 catalytic time 30 min, the precipitate with nickel content 11.15 % was obtained, and Ni catalyst can be separated by magnetic separation with nickel recovery ratio of 99.52 %. Ni2+ in SpHR precipitates to Ni(OH)2 and then disintegrates and reduces to Ni, and Ni + NiSO4 stepwise catalysis includes two steps of pre-catalysis and secondary catalysis. After fourth cyclic experiment, the vanadium content of V2O3 product obtained was 67.46 % (i.e. 99.21 % V2O3 purity met the requirements of GB 40301–2021), the total recovery was 98.68 %, and the vanadium loss ratio was stable at 1.22 %. The process of SpHR has no ammonia nitrogen wastewater or waste gas discharge, and the price of V2O3 with purity more than 99 % on the market is about 260,000 ¥/t. The stepwise catalysis SpHR has remarkable environmental benefits and economic benefits.

All Printed Photoanode/Photovoltaic Mini-Module for Water Splitting.

Printing a large-area bismuth vanadate photoanode offers a promising approach for cost-effective photoelectrochemical (PEC) water splitting. However, the light absorption trade-off with charge transfer, as well as stability issues always lead to poor PEC efficiency. Here, the solution-processed recipe is advanced with BiI3 dopant for the printed deposition with controllable crystal growth. The resultant BiVO4 films prefer (001) orientation with nanorod feature on substrate, allowing a faster charge transfer and improved photocurrent. The BiVO4 photoanode in tandem with perovskite solar module delivers an operating photocurrent density of 5.88mA cm-2 at zero bias in 3.11 cm2 active area under AM 1.5 G illumination, yielding a solar-to-hydrogen efficiency as high as 7.02% for unbiased water splitting. Equally important, the stability of the aged BiVO4 rods has been addressed to distinguish phase segregation at surface. The photocatalysis degradation composes of vanadium loss and Bi2 O3 enriching at the surface, opening a lid on the long-term stability of BiVO4 photoanodes.

Preparation of high-quality FeV50 alloy by an improved SHS-EAH multi-stage process

As the most widely used vanadium intermediate alloy, ferrovanadium is mainly prepared by the self-propagating high-temperature synthesis (SHS) process with the advantages of short process and large heat release. However, there is a trade-off between the amount of reduction agent of Al and the product quality of ferrovanadium, which is caused by the thermodynamic equilibrium limitation of the reduction between Al and vanadium oxides. The reasonable adjustment of the trade-off has become an urgent problem to be solved for the preparation of high-quality ferrovanadium. In the present work, the thermodynamic equilibrium for the reduction limitation using Al as reducing agent has been thoroughly analyzed with the reference to the equilibrium phase diagram. It was found that the theoretical reduction limitation of total vanadium (T.V) in slag was decreased from 4.08 wt.% to wt. 0.86 wt.% when the Al content in alloy reached 2.0 wt.% at 1800 °C. The vanadium in slag was mainly presented in the form of MgV3O8 and coexisting with other phases of MgAl2O4, CaAl2O4, CaAl4O7, CaAl12O19. With the purpose of further decrease the high Al concentration in alloy and vanadium loss in slag, an improved SHS-EAH process was implemented by multi-stage gradient aluminum addition coefficient pattern, the average vanadium content in slag was reduced from 1.82 wt.% to 0.83 wt.%, while the aluminum content in FeV50 alloy was decreased from 1.5 wt.% to 0.4 wt.%. The SHS-EAH process was proved to be a better process with improved yield and quality for the preparation of ferrovanadium.

Soil covering measure mitigates vanadium loss during short-term simulated rainfall in the vanadium titano-magnetite tailings reservoir

Soil covering is an operative measure to decline pollutant release in tailings reservoirs and promote vegetation restoration, yet urgent research still needs to probe into pollutant leaching and migration in the artifact technology under extreme precipitation. Here, a soil column leaching experiment was designed to explore the migration and behaviors of vanadium (V) in the system of vanadium titano-magnetite tailings (VTMTs) covered by soils with different depths (5 cm, 10 cm, and 15 cm). Chemical fractions of V in the VTMTs and covered soils were analyzed to decipher the mechanisms underlying the V migration. We found a limited V leaching (0.26–0.52 μg/L, <0.01% of total V) in the columns during the experiments, and V in the VTMTs was not apt to be leached or migrate upward to the overlying soils. The soil volumes overlaid had nonsignificant effect on the V behaviors in the VTMTs (P > 0.05), because of the dominant and stable residual V (96.4% of total V) in the tailings. Although acid soluble V might be transformed to oxidizable V, it was resupplied by the fractions of weak-bound V in the solid phases during the leaching experiments. The mineral metal (hydr)oxides (e.g., aluminum, iron) determined the V behaviors in the VTMTs via absorption effect, and the high affinity of V to organic matters probably prevented its migration throughout the overlying soils. The results indicate that soil covering measure in the VTMTs reservoirs effectively reduces V migration or release from the tailings through leaching or upward migration, which provides a significant guidance for vegetation restoration in V-rich tailings reservoirs.

Water leaching of roasted vanadium slag: Desiliconization and precipitation of ammonium vanadate from vanadium solution

This research investigated water leaching of roasted vanadium slag and studied the effects of leaching parameters, such as agitation speed, temperature, liquid-to-solid ratio, and leaching time. Further, solution purification via desiliconization and precipitation of ammonium vanadate were studied using the vanadium solution obtained from the water leaching of roasted vanadium slag. Vanadium solution contains residual silicon (1.67 g/L), which should be removed before ammonium vanadate precipitation. Based on the results, vanadium can be effectively recovered from vanadium slag and a recovery efficiency of 96.9% was obtained under optimal water leaching conditions. During solution purification, silicon can be precipitated with Al2(SO4)3 to very low levels without any significant vanadium loss. The ammonium vanadate precipitation achieved a high precipitation efficiency of >99%.

Dynamic Study on Vanadium Extraction Process in Basic Oxygen Furnance: Modeling Based on Gibbs’ Free Energy Minimization

Vanadium extraction process demands low residual vanadium and carbon loss, and variations of dissolved elements in hot metal must be determined to achieve it. A three parts dynamic model that applies the concept of Gibbs’ free energy minimization at the slag–metal interface is proposed. Modeling simulation results shows good uniformity with plant experimental data, and the presented model can describe the vanadium extraction process in BOF qualitatively well. The effects of coolant addition and oxygen flow rate have been studied by modeling. The lack of coolant will reduce (FeO) content and elevate the molten bath temperature, which are harmful to deep vanadium removal with less carbon loss in semi-steel. The excessive oxygen flow rate has little effect on residual [V], and there is more carbon loss because of higher (FeO) content and molten bath temperature.

Controlled Hydrothermal Precipitation of Alunite and Natroalunite in High-Aluminum Vanadium-Bearing Aqueous System

During the acid leaching process of black shale, with the destruction of the aluminosilicate mineral structure, a large amount of aluminum (Al) is leached, accompanied by the release of vanadium (V). To separate aluminum from the vanadium-containing solution, the precipitation behavior of aluminum ions (Al3+) was investigated under hydrothermal conditions with the formation of alunite and natroalunite. In the solution environment, alunite and natroalunite are able to form stably by the Al3+ hydrolysis precipitation process at a temperature of 200 °C, a pH value of 0.4 and a reaction time of 5 h. When Al3+ was precipitated at a K/Al molar ratio of 1, the aluminum precipitation efficiency and the vanadium precipitation efficiency were 64.77% and 1.72%, respectively. However, when Al3+ was precipitated at a Na/Al molar ratio of 1, the precipitation efficiency of the aluminum decreased to 48.71% and the vanadium precipitation efficiency increased to 4.36%. The thermodynamics and kinetics results showed that alunite forms more easily than natroalunite, and the reaction rate increases with increasing temperature, and the precipitation is controlled by the chemical reaction. Vanadium loss increases as the pH value increases. It can be deduced that the ion state of tetravalent vanadium (VO2+) was transformed into the ion state of pentavalent vanadium (VO2+) in the hydrothermal environment. The VO2+ can be adsorbed on the alunite or natroalunite as a result of their negative surface charges, ultimately leading to vanadium loss.

Directional conversion and removal of complex phosphorus compounds from acidic leaching solution containing vanadium

Deep phosphorus removal from acidic leaching solution containing vanadium is a challenging problem due to the formation of complex phosphorus compounds. This problem can be possibly solved by proposed hydrogen peroxide coupled with iron-aluminum mixed salts, in which complex phosphorus compounds can be directionally converted and removed. Under the optimal conditions (the mole ratio of Fe/Al/P at 1.25:0.40:1.00, initial pH value at 5.00, reaction time for 1 h, reaction temperature at 70℃, the mole ratio of H2O2/P of 20:1), the phosphorus removal efficiency and vanadium loss rate were 99.29 % and 5.96 %, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy were used for characterization analyses of phosphorus in the removal products. Results indicated that hydroxyl radicals (·OH) made the directional conversion of complex phosphate radicals to PO43-. Complex phosphorus compounds were eventually removed in the form of PO43-. An efficient phosphorus removal progress was obtained. The concentration of residual phosphorus in solution was only 3.7 mg/L, and the mole ratio of vanadium to phosphorus in solution changed from 18 to 2353.

Examining the effects of nitrogen-doped carbon coating on zinc vanadate nanoflowers towards high performance lithium anode

Coating transition metal oxides with nitrogen-doped carbon is an efficient way to enhance lithium-ion battery performance by improving the conductivity and stability of the electrodes. So far, little attention has been paid to how the calcination process affects bimetallic oxides, such as zinc vanadate, with regards to the oxidation state of the metal, the zinc/vanadium ratio and the specific surface area. In this work, we report nitrogen-doped carbon coated zinc vanadate nanoflowers (particle size: 10 nm; coating layer thickness: 20 nm) with a high specific surface area (115 m2 g−1) through a facile method. High-angle annular dark-field scanning transmission electron microscopy, X-ray diffraction and electron paramagnetic resonance spectroscopy reveal that V5+ from the precipitated Zn3(OH)2(V2O7)(H2O)2 is largely converted to V3+ in ZnV2O4. A vanadium loss of about 9% during calcination lead to increased Zn/V ratio and formation of ZnO. When applied as anode in a lithium-ion battery, the as-prepared ZnV2O4/ZnO@N doped C exhibits a considerable reversible specific capacity of 620 mAh g−1 at a current density of 0.1 A g−1 after 50 cycles, very close to the theoretical capacity (651 mAh g−1) and considerably higher than the non-coated counterpart (306 mAh g−1). The material is stable during extended cycling (200 cycles at 0.5 A g−1). In-depth electrochemical analysis including three-electrode system testing shows that the carbon shell is crucial in maintaining the structure stability and enhancing the capacity of the active material.

Influence of the sintering process on microstructures and microwave properties of Ca5Ni2Mg2V6O24 ceramics

A new low-temperature sintered microwave ceramic Ca5Ni2Mg2V6O24 (CNMVO) was synthesized by a solid-state reaction method. The effect of sintering process on microstructures and microwave properties of CNMVO ceramics was investigated in detail. XRD results and EDS analyses show that CNMVO ceramics sintered at 850–925 °C are the uniform solid solution with a stable cubic garnet structure. The CNMVO ceramic sintered at 875 °C has the highest Q × f value and is accompanied by the volatilization of vanadium observed by SEM. TG curves demonstrate that the increase of heating rate weakens the vanadium loss. According to the Raman spectra, the Q × f value reaches the maximum value at a heating rate of 2 °C/min, because of the highest cation ordering degree and the densest packing fraction caused by the properly deficient vanadium. As a result, the Ca5Ni2Mg2V6O24 ceramic sintered at 875 °C with a heating rate of 2 °C/min exhibits the best microwave properties: εr = 8.07, Q × f = 60,613 GHz, and τf = −32 ppm/°C.

Effects of different alkalis on the behaviour of vanadium loss in the pretreatment of vanadium-bearing acid leaching solution

Effects of different alkalis on the behaviour of vanadium loss in the pretreatment of vanadium-bearing acid leaching solution

Separation and recovery of iron impurity from a vanadium-bearing stone coal via an oxalic acid leaching-reduction precipitation process

Sulfuric acid leaching solutions of vanadium-bearing stone coal usually contain massive iron impurity, which is detrimental to vanadium extraction because iron is easy to precipitate or co-extracted during the solvent extraction and ion exchange. Meanwhile, sulfuric acid in wastewaters is environmentally hazardous. In this paper, a vanadium-bearing stone coal was leached with oxalic acid, which has the advantages of cheap biological sources and good environmental compatibility. The iron impurity was separated from the oxalic-acid leaching vanadium-bearing solution (OLVS) via reduction precipitation. During the oxalic acid leaching, 80.5% of the vanadium can be recovered, and 50.2% of the iron impurity was leached with vanadium under the conditions: a CaF2 addition of 5 wt%, an oxalic acid dosage of 60 wt%, a leaching time of 4 h, a leaching temperature of 95 °C and a water-mineral ratio of 1.0 mL/g. However, the concentrations of vanadium and iron were 1777.5 ppm and 6552.5 ppm, respectively, in the OLVS. By adopting reduction precipitation, 83.8% of the iron was precipitated as FeC2O4·2H2O with only a 2.5% vanadium loss when an iron powder dosage was 2.5 times that of the stoichiometry for 90 min at 25 °C. The oxalic-acid leaching vanadium-bearing solution after reduction precipitation (OLVS-P) contained 1733.6 ppm of vanadium and only 1059.8 ppm of iron. Analyses indicated that the as-produced FeC2O4·2H2O (P-FeC2O4·2H2O) was in a high crystalline state with a purity of 98.2%. Therefore, the iron impurity can be separated and recovered from the vanadium-bearing stone coal via the oxalic acid leaching-reduction precipitation process.

STUDY OF THE NATURE OF THE VANADIUM VOLATILIZATION FROM BLAST FURNACE AT SMELTING TITANOMAGNETITES

Nature and amount of vanadium losses with blast furnace throat gas have been studied. It has been estimated that vanadium loss with furnace throat dust and slag is considerably higher that ablation from the iron stove. It has been stated that a part of vanadium gets alkalined and converted into solution in the process of wet gas clearing. Vanadium losses through the furnace throat are equal or even prevail over vanadium losses with slag.

A Novel Process of Vanadium Extraction from Molten Vanadium Bearing Slag

In this study, a novel process (melting process) of vanadium extraction from vanadium slag (V-slag) in its molten state was attempted at the laboratory scale by oxidizing slag with pure oxygen in the presence of sodium carbonate (Na2CO3). The effect of Na2CO3 content in the slag on the vanadium extraction was studied. The sintered samples were then leached by water and characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. The results showed that vanadium-rich phases, mainly NaVO3 and Na9V14O35 were formed in the melting process. About 80 % of the vanadium recovery was obtained by addition of 25 % Na2CO3 under certain leaching conditions (i.e. 85 % of the particle size <150 μm, leaching temperature 95 °C, leaching time 2 h, liquid to solid ratio 5:1 mL/g, stirring speed 500 rpm), which is in the same level comparing with the roast process. The side reactions could be easier to occur at elevated temperatures, causing more sodium salt consumption and vanadium loss. The overall vanadium loss was mainly attributed to the insufficient oxidizing reaction of V(IV) to V(V). Compared to the roast process, recovery of vanadium by the present melting process from V-slag and utilization of its heat energy are of significant importance not only for saving metal resources, but also for energy saving and emission reduction.

Laboratory Studies of Vanadium Precipitation with Flue-Gas Sulfuric Acid

The exploratory experiments of precipitating vanadium which simulated the process conditions in a vanadium plant with the indexes of vanadium loss and the cost were tested with industrial sulfuric acid and flue-gas sulfuric acid in laboratory, respectively. The technology optimizations were studied by selecting the experimental group with the lowest vanadium loss and cost. The results indicate that the vanadium loss and cost are the lowest by one-step vanadium precipitation with flue-gas sulfuric acid, and the optimum processes are as follows: the pH of solution is adjusted to 2.2 after adding the vanadium precipitation agent; the precipitation is proceeded 1 hour at 99°C or 100°C. The vanadium loss and cost per 1000 kg V2O3 are respectively 3.06 kg and 763.18 yuan by the optimum processes, which are much less than the processes with industrial sulfuric acid.

Effect of colloidal potassium alum formation on vanadium recovery from acid leach solutions of stone coal

The nattier-blue colloidal particles precipitated out from the sulfuric acid leach solution of stone coal were identified to be potassium alum (KAl(SO4)2·12H2O). The particles were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM) and theoretical analysis with thermodynamics of ion crystallization. The results show that the particles belonged to potassium alum with micro-scale granular surfaces. The colloidal potassium alum formed with the temperature of the leaching solution cooling to 45°C. This observation could lead to 27.6% vanadium loss in the vanadium extraction process, which might be attributed to the chemical adsorption of vanadium in the form of the species of VO2+ on the potassium alum surfaces.

Vaporization Studies from Slag Surfaces Using a Thin Film Technique

The investigations of vanadium vaporization from CaO-SiO2-FeO-V2O5 thin film slags were conducted using the single hot thermocouple technique (SHTT) with air as the oxidizing atmosphere. The slag samples were analyzed after the experiments by SEM/EDX. The vanadium content was found to decrease as a function of time. The loss of vanadium from the slag film after 30 minutes of oxidation was approximately 18 pct and after 50 minutes, it was nearly 56 pct. The possible mechanism of vanadium loss would be the surface oxidation of vanadium oxide in the slag, VOx to V5+, followed by surface evaporation of V2O5, which has a high vapor pressure at the experimental temperature.

Photofragmentation of mass-selected vanadium doped cobalt cluster cations

The stability of mass-selected vanadium doped cobalt cluster cations (Co n−1V+, n = 11–21 and Co13−m V m +, m = 0–3) is studied by photofragmentation. The clusters are produced by pulsed laser vaporization, mass-separated in a dual reflectron time-of-flight mass spectrometer, and photodissociated using the second harmonic of a Nd:YAG laser. The recorded fragmentation spectra show that all studied clusters prefer dissociation by loss of a cobalt atom. Sequential cobalt atom evaporation is found at higher laser fluences. No dissociation channel involving vanadium loss is observed, consistent with the V-Co bonds being stronger than the Co-Co bonds. Co12V+, which was predicted to have an icosahedral symmetry, is found to be the most stable cluster among the singly vanadium doped species. Consecutive increment of the vanadium concentration along the Co13 − m V m + (m = 0–3) series further confirms the enhanced stability of Co12V+, in excellent agreement with theoretical predictions [S. Datta, M. Kabir, T. Saha-Dasgupta, A. Mookerjee, Phys. Rev. B 80, 085418 (2009)].

Dephosphorization of Vanadate Leaching Solution by Chloride-Free Dephosphorizing Agent

CaCl2 was generally used as dephosphorizing agent during the sodiumization-vanadium extraction process. However, a large number of chloride ions were brought into wastewater from vanadium precipitation, which increased the corrosion of the evaporation-concentration equipments of wastewater treatment. Then, the chloride-free dephosphorizing agent (CFDA) was developed, and the dephosphorizing effect was compared with that of CaCl2. The results showed that, with the chloride-free dephosphorizing agent, the dephosphorizing ratio≥99 %, clarification time of 120 min, vanadium loss≤3.5 %, and vanadate leaching solution dephosphorized by the CFDA could meet the demand of high density vanadium precipitation.